The present invention relates to an automatic transmission.
There exists an automatic transmission that is mounted in a vehicle such as a front engine rear drive (FR) type. A torque converter is coaxially arranged between an output shaft (a crankshaft) of the engine and a propeller shaft transmitting a rotation to the rear wheels in the vehicle. The torque converter is connected to the output shaft of the engine, and to a speed change mechanism that shifts a rotation of the torque converter and transmits the rotation to the propeller shaft.
In the speed change mechanism, the input shaft and the output shaft are rotatably fitted directly or via an intermediate shaft. A single-shaft aligned center axis is structured by the shaft in a both-end support state by a case, a gear mechanism including rotary members such as each gear of the planetary gears, a hub member connecting these gears, a sleeve member, a (clutch) drum member, and the like. In addition, among these rotary members, rotary members, except for what are fixed on the center axis (the input shaft, the intermediate shaft, and the output shaft), are rotatably supported on the center axis by a sleeve or a needle bearing and the like and are also supported in the axial direction by a thrust bearing and the like interposed among each rotary member.
By the way, the propeller shaft generates torsion because a rotational torque acts when it transmits a driving rotation. The changes of torsion magnitude by torque variation cause expansion and contraction. Therefore, for example, a pressing force and a tensile force are applied to the output shaft fixed in the propeller shaft via a flange yoke and the like from the axially rear side. In particular, when the output shaft is pressed from the rear side and moves to the front side, there is a possibility that the input shaft moves via a thrust bearing and the like interposed among the rotary members. The torque converter provided with a lock-up clutch is affected on the axial position of the lock-up clutch. Therefore, it is possible for a slip to occur at the time of non-engagement, and controllability in an engagement control (a slip control) is adversely affected.
Therefore, there has been proposed a ball bearing that rotatably supports the output shaft in the axial direction (see, for example, German Patent Application Laid-Open No. 10230861 (DE10230861A1)). This positions and fixes an outer race of the ball bearing for the case, pinches an inner race of the ball bearing by a flange yoke for the output shaft by fastening a backward nut, and also positions and supports the axial position of the output shaft by the ball bearing.